DOH! Severums. the one other commonly available SA cichlid that is not readily identifiable. Well I still HIGHly doubt that the limestone did it. Limestone will raise ph and alkalinity, but no not think it would raise it so fast as to shock a fish. Plus, you said you were out in the country? Are you on well water? Depending on where you live, your water could be harder than limestone would make it anyway.
Sometimes fish do not acclimate well and as a result, they die. This is even more true of older fish. don't beat yourself up. You tried to find help. You did the water changes. There really isn't much more you could have done. what other fish are in the tank btw?
Sometimes fish do not acclimate well and as a result, they die. This is even more true of older fish. don't beat yourself up. You tried to find help. You did the water changes. There really isn't much more you could have done. what other fish are in the tank btw?